Three-dimensional Excitation-emission Matrix Spectra Research Articles

Compositions, sources, and bioavailability of colloidal organic matter in Lake Taihu

Colloidal organic matter (COM) exists ubiquitously in natural waters, and plays a pivotal role in biogeochemical cycles. Lake Taihu is confronted with severe eutrophication and algal blooms. Field investigations were carried out in Lake Taihu and two inflow rivers for two years to identify the source of COM and explore the bioavailability of COM to algae. Compositions and sources of COM were analyzed through UV absorption coefficients and parallel factor analysis of three-dimensional excitation emission matrix spectra (3D EEMs-PARAFAC). Absorption coefficient a(350) of COM in rivers surpassed that in the lake, SUVA254 exhibited noteworthy seasonal variations, and SR indicated a stable autochthonous characteristic. Three components were identified by PARAFAC analysis: tryptophan-like (C1), humic-like (C2), and tyrosine-like (C3). Fluorescence indexes showed that C1 and C3 were mainly autochthonously produced and C2 was derived from allochthonous inputs. The bioassays were conducted to assess the bioavailability of COM to the dominant species, Microcystis aeruginosa. The results showed that colloids supplied rich carbon sources and trace metals, supporting the growth of Microcystis aeruginosa. The specific growth rate, Chl a content, and biological increment of Microcystis aeruginosa in 50 % colloid-added treatment exceeded those in 20 % and 75 % treatments. Simultaneously, the effective quantum yield (Fv/Fm) and the apparent photosynthetic electron transport rate (ETRmax) demonstrated that the photosynthetic activity of Microcystis aeruginosa was higher in 20 % treatment. These findings help in understanding the intricate mechanisms of COM in lake ecosystems, and provide the robust scientific foundation for water management and protection in Lake Taihu.

Characterization and recognition of three-dimensional excitation-emission matrix spectra of wastewater from six typical categories

In this study, we analyzed the characteristics of three-dimensional excitation-emission matrix spectra (EEMs) of 150 samples from five industrial wastewater types and domestic sewage to track water pollution sources effectively. We then developed a recognition model for wastewater EEMs by establishing a feature dataset containing fluorescence peak values and parameters derived from EEMs, integrated with machine learning techniques. This model enables the rapid and precise identification of pollution sources. Our findings suggest that although the EEMs of the six wastewater categories are distinct, visual differentiation is challenging. This was confirmed by cosine similarity assessments, showing some samples with low within-group (< 0.8) and high between-group (> 0.95) similarities. Despite significant variations in EEMs features across wastewater categories, identifying specific pollutants remains difficult, especially for pulp mills and leather effluents. Among the tested classification algorithms, Support Vector Machine (SVM) achieved the highest performance with 91.7 % accuracy, 94 % precision, 91 % recall, and 92 % F1-score, outperforming K-Nearest Neighbors and Partial Least Squares Discriminant Analysis. The SVM significantly improved identification accuracy for pulp mill and leather processing wastewaters compared to other models. To enhance identification accuracy, further exploration of EEMs features and expanding the training dataset are recommended. Combining EEMs features with machine learning presents a promising method for improving water pollution supervision and source tracing in environmental management practices.

Extracting extracellular polymeric substances from fungi in contrasts: from quantity to quality

Many fungi are able to produce extracellular polymeric substances (EPS) for environmental, food, and industrial applications. This study evaluated the extraction (in vivo) of EPS from Rhodotorula mucilaginosa, a typical yeast with abundant EPS. Three extracting methods were set, i.e., heating, addition of NaCl during heating, and cation exchange resin (CER). The abundance of extracted proteins and polysaccharides showed evident contrasts (elevatedto ~ 600 and 1700 mg/L, respectively) after heating at 70 °C in water. Although the higher temperature will increase the extracted abundance of EPS, the leakage of DNA would be enhanced due to cell rupture. The addition of NaCl further promoted the efficiency of extraction, either for proteins (from ~ 550 to ~ 650 mg/L) or polysaccharides (from ~ 1700 to ~ 2010 mg/L). Moreover, the biochemical results showed that the extracted abundance of EPS via heating was dramatically higher than that via CER. Additionally, DNA leakage in the CER treatment (2.0 g/g DW) was significantly higher (up to > 6 mg/L) than that under heating at 70 °C (< 2 mg/L). Furthermore, the three-dimensional excitation-emission matrix spectra showed two characteristic peaks of emission/excitation wavelength at 280/300 and 280/350, suggesting the relative high diversity of organic matters in EPS after heating treatments. Finally, a fluctuation of polysaccharide abundance in EPS at 500-1500 mg/L Pb2+ level was elucidated by the extraction based on heating treatment. This study hence confirmed that the heating method might be recommended for extraction of EPS from fungi in vivo KEY POINTS: • 3D-EEM results indicated that heating could extract more EPS compared with CER. • Heating treatments showed lower DNA leakage from fungi than CER treatments. • Addition of NaCl promoted the detachment of EPS from fungal cells in vivo.

Efficient degradation of tetracycline by singlet oxygen-dominated peroxymonosulfate activation with magnetic nitrogen-doped porous carbon

Nonradical reaction driven by peroxymonosulfate (PMS) based advanced oxidation processes has drawn widespread attention in water treatment due to their inherent advantages, but the degradation behavior and mechanism of organic pollutants are still unclear. In this study, the performance, intermediates, mechanism and toxicity of tetracycline (TC) degradation were thoroughly examined in the constructed magnetic nitrogen-doped porous carbon/peroxymonosulfate (Co-N/C-PMS) system. The results showed that 85.4% of TC could be removed within 15 min when Co-N/C and PMS was simultaneously added and the degradation rate was enhanced by 3.4 and 14.7 folds compared with Co-N/C or PMS alone, respectively. Moreover, the performance of Co-N/C was superior to that of most previously reported catalysts. Many lines of evidence indicated that Co-N/C-PMS system was a singlet oxygen-dominated nonradical reaction, which was less interfered by pH and water components, and displayed high adaptability to actual water bodies. Subsequently, the degradation process was elaborated on the basis of three-dimensional excitation-emission matrix spectra and liquid chromatography-mass spectrometry. At last, the toxicity of treated TC was greatly reduced by using microalgae Coelastrella sp. as ecological indicator. This study provides a promising approach based on singlet oxygen-dominated nonradical reaction for eliminating TC in water treatment.

Magnetic flocculation of algae-laden raw water and removal of extracellular organic matter by using composite flocculant of Fe3O4/cationic polyacrylamide

Algae-laden water with low turbidity is a critical problem in eutrophic lakes of arid regions. Thus, how to effectively separate algae and turbidity is an urgent problem for drinking water production. In the current study, the magnetic flocculation performance of algae-laden raw water purification was investigated by using magnetic composite flocculant Fe3O4/cationic polyacrylamide (CPAM). The Chlamydomonas sp., turbidity and UV254 removal efficiency were evaluated at different Fe3O4: CPAM mass ratios, dosages and pH values. The recovery and reusability of Fe3O4/CPAM in flocculation was tested. Moreover, the saturation magnetization of flocculants and flocs and zeta potential of supernatant in magnetic separation was examined, and the flocculation mechanism of Chlamydomonas sp. was explored accordingly. In addition, the removal efficiency of bound extracellular organic matter (BEOM) and dissolved extracellular organic matter (DEOM) was compared by using Fe3O4/CPAM. The flocculation mechanism and interactions between Fe3O4/CPAM and extracellular organic matters were analyzed according to ultraviolet (UV) spectra, fluorescence three-dimensional excitation emission matrix spectra (EEM), gel permeation chromatography (GPC), and X-ray photo electronic spectroscopy (XPS). Results show that more than 97% of chlorophyll a (Chla), 87% of turbidity, and 65% of UV254 were removed at Fe3O4/CPAM dosage of 1.2 mg/L, Fe3O4: CPAM mass ratio of 1.5:1.0, and pH of 4.0–9.0. Charge neutralization was dominant at pH < 9.0, whereas adsorption through hydrogen bond played an important role at pH > 9.0. Humic acid-like substances and tryptophan-like proteins were the main components of DEOM, whereas fulvic acid-like substances, tryptophan-like proteins and few polysaccharides existed in BEOM. Fe3O4/CPAM exhibited excellent performance in binding with the functional groups in tryptophan-like proteins, such as amino, carboxyl and hydroxyl groups.

Mg2+ distribution in activated sludge and its effects on the nitrifying activity and the characteristics of extracellular polymeric substances and sludge flocs

Abstract Divalent cations act as bridges among extracellular polymeric substances (EPS) and form cross-linkage for the self-immobilization of microbial biomass. However, their effects on the nitrification performance during the biological nitrogen removal are still unclear. In the present study, the effects of Mg2+ on the nitrifying activity, EPS and floc characteristics were investigated using a lab-scale sequencing batch reactor. The distribution of Mg2+ was quantified at different level of sludge floc. The results indicated that the nitrification activity was significantly improved when influent Mg2+ was below 1.1 mmol/L, but suppressed at 3 mmol/L. The overall performance characterized by COD, NH4+-N and TN, the particle size and sludge flocculation ability rapidly increased with the increase of Mg2+ concentration. Mg2+ was mainly distributed in the pellet and changed slightly in supernatant, LB-EPS and TB-EPS. The four fluorescence peaks detected by three-dimensional excitation-emission matrix spectra were attributed to PN-like substances and humic acid-like substances in the LB-EPS and TB-EPS. The results of XPS analysis demonstrated that LB-EPS and TB-EPS comprised similar elements. Therefore, the types of EPS functional groups was unchanged under varied Mg2+ concentrations, while their proportions changed and LB-EPS/EPS was key factor for the changes of bioflocculation.

Recognizing Dissolved Organic Matter with an Improved Fluorescence Regional Integral Method

The aim of this paper was to study transformations of Dissolved Organic Matter (DOM) in marl rock groundwater. To achieve this, we carried out a series of soil column experiments, using a DOM solution as the water sample and marl rock as the testing rock sample. Three-Dimensional Excitation-Emission Matrix Spectra (3DEEMS) were generated for DOM solutions and the Analytic Hierarchy Process (AHP) was introduced to improve the traditional method of fluorescence regional integral (TMFRI). We termed this approach the Improved Method of Fluorescence Regional Integral (IMFRI) and used it to identify the type of DOM in the marl rock. The result shows that DOM recognition using TMFRI is only 50% accurate and consequently transformations are hard to recognize. In contrast, our results show that use of IFRIM has a DOM type recognition accuracy of 83.33% and so this method can be used with confidence to describe transformation characteristics. And we find that in the marl rock, the leaching test showed a new fluorescence peak at 312 h and the humic acid was degraded into soluble microbial products by microorganisms.

Bisphenol S Adsorption Behavior on Ferralsol and Biochar Modified Soil with Dissolved Organic Matter.

Bisphenol S (BPs) has been found in a variety of common consumer products surrounding human living, despite the fact that it could damage the human digestive system and genital system. In China, straw-returning to the field is a common soil improvement technology used to increase the concentration of dissolved organic matter (DOM), which plays an important role in the natural environment as a microreactor of contaminants. Additionally, the biochar obtained by the straw is an effective soil conditioner. DOM is a key influencing factor when biochar is employed as the conditioner of BPs contaminated soil. However, the BPs adsorption behavior on the Ferralsol affected by DOM and biochar is also unclear. Hence, DOM was prepared and the effect of DOM on the BPs adsorption behavior on soil and biochar modified soil was investigated. DOM was characterized by Elemental analysis, Fourier transforming infrared spectra (FT-IR), and three-dimensional excitation-emission matrix spectra (3D-EEM). The results of the adsorption experiments indicated that both biochar and DOM could improve the BPs adsorption capacity in Ferralsol, while DOM suppressed the BPs adsorption capacity of biochar modified soil, indicating that DOM and BPs could not be applied at the same time for BPs adsorption.

Characterization of CDOM in saline and freshwater lakes across China using spectroscopic analysis

Colored dissolved organic matter (CDOM) is a major component of DOM in waters, and plays a vital role in carbon cycling in inland waters. In this study, the light absorption and three-dimensional excitation-emission matrix spectra (EEMs) of CDOM of 936 water samples collected in 2014–2017 from 234 lakes in five regions across China were examined to determine relationships between lake water sources (fresh versus saline) and their fluorescence/absorption characteristics. Results indicated significant differences regarding DOC concentration and aCDOM(254) between freshwater (6.68 mg C L−1, 19.55 m-1) and saline lakes (27.4 mg C L−1, 41.17 m-1). While humic-like (F5) and fulvic-like (F3) compounds contributed to CDOM fluorescence in all lake waters significantly, their contribution to total fluorescence intensity (FT) differed between saline and freshwater lakes. Significant negative relationships were also observed between lake altitude with either F5 (R2 = 0.63, N = 306) or FT (R2 = 0.64, N = 306), suggesting that the abundance of humic-like materials in CDOM tends to decrease with increased in lakes altitude. In high-altitude lakes, strong solar irradiance and UV exposure may have induced photo-oxidation reactions resulting in decreased abundance of humic-like substances and the formation of low molecular weight compounds. These findings have important implications regarding our understanding of C dynamics in lacustrine systems and the contribution of these ecosystems to the global C cycle.

Comparison between humic-like peaks in excitation-emission matrix spectra and resin-fractionated humic substances in aquatic environments

The intensity of the 340/430-nm peak in the three-dimensional excitation-emission matrix spectra of water samples has been used as an index of the concentration of aquatic humic substance (AHS). However, whether this peak corresponds uniquely to AHS has not been definitively verified. Therefore, in this study, our objectives were: (1) to determine whether the 340/430-nm peak in the spectra of lake and river water samples does, in fact, correspond uniquely to AHS; (2) to determine what type of dissolved organic matter (DOM), in terms of hydrophobicity, accounts for the peak; and (3) to determine the advisability of using excitation-emission matrix spectroscopy to rapidly estimate AHS concentrations. We found that the 340/430-nm peak originates not only from the AHS fraction of DOM but also from a portion of the hydrophilic fraction. By analyzing the quantitative relationship between AHS concentration and 340/430-nm peak intensity for DOM samples, we found the intensity can be used to estimate AHS concentration in lake water when the concentration is strongly affected by influent river water or when the ratio of ultraviolet (UV) absorbance to dissolved organic carbon concentration is relatively high.

Characteristics of Water Extractable Organic Nitrogen from Erhai Lake Sediment and Its Differences with Other Sources

The 47 samples from Erhai Lake surface sediments were collected in different seasons. The distribution and structure characteristics of sediment water extractable organic nitrogen(WEON) were investigated by using the combined techniques of UV-Vis absorption and three-dimensional excitation-emission matrix spectra(3DEEMs). The differences in DON of various sources(overlying water, pore water, inflow Rivers and wet deposition) were explored to analyze its effects on sediment. The results showed that:1the temporal distribution followed the pattern of summer > spring > autumn > winter, with the spatial WEON distribution of northern > southern > central. 2 The humic degree of Erhai sediment WEON was relatively high and mostly composed of fulvic acid, which mainly contained UV-like humic-like fluorescence peak A and high-excited tryptophan fluorescence peak B. This indicated that it was mainly affected by terrestrial input and microbial activity. 3 There were two fluorescent components(C1, C2) in the sediments and other sources of Erhai Lake. The component C1 was the endogenous visible ultraviolet peak formed by biodegradation, while the component C2 was the tryptophan peak. The bioavailability of wet deposition samples was comparatively high, greatly impacting Erhai Lake in heavy rainfall. The DON bioavailability in the inflow river was the lowest, which was prone to be accumulated in sediments. 4The DON component C1 and C2 in overlying water had significant negative correlation with Erhai sediment WEON contents(r=-0.79, P<0.01;r=-0.944, P<0.01). This suggested that the overlying water DON components could indirectly reflect the sediment WEON content of Erhai Lake, namely the higher the fluorescence components C1 and C2 in overlying water DON were, the lower the sediment WEON content was.

Flocculation and antimicrobial properties of a cationized starch

In this study, a series of cationized starch-based flocculants (starch-3-chloro-2-hydroxypropyl triethyl ammonium chloride, St-CTA) containing various quaternary ammonium salt groups on the starch backbone were prepared using a simple etherification reaction. All of the prepared starch-based flocculants show effective performance for the flocculation of kaolin suspension, two bacterial (Escherichia coli and Staphylococcus aureus) suspensions, and two contaminant mixtures (kaolin and each bacterium) under most pH conditions. St-CTA with a high substitution degree of CTA demonstrates improved contaminant removal efficiency because of the strong cationic nature of the grafted quaternary ammonium salt groups and the charge naturalization flocculation effect. The antibacterial effects of St-CTA were also evaluated, considering that many quaternary ammonium salt compounds elicit bactericidal effects. Three-dimensional excitation–emission matrix spectra and direct cell morphological observation under scanning electron microscopy reveal that the starch-based flocculants exhibit better antibacterial effects on the Gram-negative bacterium E. coli than on the Gram-positive bacterium S. aureus. The thicker cell wall due to the presence of abundant peptidoglycan and teichoic acids of S. aureus than E. coli explains the uneasy breakage of S. aureus cell wall after being attacked by the cationized starch-based flocculants.

Flocculation performance of cationic polyacrylamide with high cationic degree in humic acid synthetic water treatment and effect of kaolin particles

Abstract In current research, the flocculation performance of cationic polyacrylamide flocculant PAMC with high cationic degree was investigated in HA synthetic water treatment, and the effect of kaolin particles was studied in kaolin-HA flocculation. Influencing factors, such as pH, PAMC dosage, initial HA concentration, cationic degree, stirring speed and stirring time, were investigated and optimized for HA removal efficiency. Two-dimensional fractal dimension of the flocs was analyzed based on flocs images, and FTIR analysis was accomplished to understand chemical structures of the flocs. Three-dimensional excitation emission matrix spectra was measured to analyze the changes in organic composition and concentraion. Finally, the HA and kaolin-HA synthetic water flocculation mechanism were studied and summarized based on analysis of zeta potential and pH. The results showed that 80.7% and 91.2% of HA removal efficiency was achieved in HA and kaolin-HA flocculation process by using 12.5 mg/L and 4–6 mg/L of PAMC, respectively. Moreover, partial colloidal HA was absorbed by kaolin particles before flocculation and was removed in flocculation through synergetic effect from kaolin particles. Charge neutralization and bridging effect was confirmed to be dominant in acidic and alkaline environment, respectively.

Formation of known and unknown disinfection by-products from natural organic matter fractions during chlorination, chloramination, and ozonation

Natural organic matter (NOM) is the main precursor of disinfection by-products (DBPs) formed during drinking water treatment processes. Previous studies of the relationships between DBP formation and NOM fractionation have mainly been focused on currently regulated DBPs and a few certain emerging DBPs. In this work, the Suwannee River NOM solution was fractionated into groups with different hydrophobicities using DAX-8 resins, and volatile and semi-volatile DBPs formed during the chlorination, chloramination and ozonation of the NOM fractions were examined by a nontargeted screening of comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry procedure. The results showed that a total of 302 DBPs representing nine chemical classes were detected, of which 266 were possibly newly detected, based on library searching with NIST 08 library (using similarity and reverse values of at least 600 and 700, respectively) and linear retention indices. The characterization of DBP precursors suggests that hydrophobic (HPO) NOM contains the major fraction of precursor for the formation of nitrogenous DBPs (contributing about 60% of the total nitrogenous DBPs) during all three disinfection processes. Much larger amounts of heterocyclic DBPs were formed from the HPO fraction than from the hydrophilic fraction during chlorination. During chloramination and ozonation, 5–15 times more ketones were formed from the hydrophilic fraction than from the HPO fraction. During ozonation, more than twice the amounts of esters and alcohols were formed from the hydrophilic fraction than from the HPO fraction. Three-dimensional excitation-emission matrix spectra suggest that similar to the formation of regulated DBPs, humic acid-like substances are probably the precursors of halogen-containing DBPs. Relatively higher nitrogenous DBPs formation from the HPO fraction might be because of the existence of protein-like materials.

Preparation of dual-function starch-based flocculants for the simultaneous removal of turbidity and inhibition of Escherichia coli in water

A dual-function starch-based flocculant, carboxymethyl-starch-graft-aminomethylated-polyacrylamide (CMS-g-APAM), was designed and prepared by a simple method. The structure and solution properties of CMS-g-APAM were characterized by fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and zeta-potential measurements. CMS-g-APAM was then applied to flocculate a kaolin suspension and an Escherichia coli suspension as well as a combination thereof. At suitable pH conditions, the starch-based flocculant not only effectively removed turbidity but it also disrupted bacterial cells. Interpretation of the zeta potential and floc properties (floc size and two-dimensional fractal structure) showed that, for the aforementioned three effluents, simple charge neutralization was the dominant mechanism of flocculation in acidic medium whereas an additional contribution from a patching effect was determined under neutral conditions. Three-dimensional excitation-emission matrix spectra and direct surface morphology observation under a scanning electron microscope both illuminated that the antibacterial activity of CMS-g-APAM involved the partial destruction of the cell wall of Escherichia coli. The mechanism can be attributed to the effective interaction between the tertiary amine group of the flocculant and the negatively charged surface of the bacterium.

Enhancing integrated removal of Microcystis aeruginosa and adsorption of microcystins using chitosan-aluminum chloride combined coagulants: Effect of chemical dosing orders and coagulation mechanisms

Abstract The effects of two chitosan (CTS)-aluminum chloride (AC) dual-coagulants with different dosing orders and a composite coagulant CTSAC (CTS and AC premixed) on removal of Microcystis aeruginosa (M. aeruginosa) cells and second metabolites in cyanobacteria-laden drinking water treatment were investigated, and in comparison with AC and CTS. Response surface methodology (RSM) was used to model and optimize the coagulation processes. The coagulation mechanisms were investigated via zeta potential, scanning electron microscope (SEM), and three-dimensional excitation-emission matrix spectra (EEM) analyses. The investigated dual/composite coagulants caused no evident damage to M. aeruginosa cells, and achieved better removal effects than coagulant individually applied. The CTSAC removed cells was the most effective for stronger entrapment and bridging ability. While the highest adsorption of extracellular microcystins (MCs) was obtained through AC–CTS (AC added firstly). CTS–AC (CTS added firstly) provided slight higher extracellular organic matter (EOM) removal. The optimal coagulation performance was obtained when CTSAC was set as 2.6 mg/L CTS plus 7.5 mg/L AC, under which 97.8% of intact cells, 53.08% of extracellular MCs and almost all EOM were simultaneously removed. Overall, the combination of CTS and AC coagulation process has proven to be a better substitute for conventional coagulation in cyanobacteria-laden drinking water treatment.

Flocculation of Escherichia coli using a quaternary ammonium salt grafted carboxymethyl chitosan flocculant.

Only few studies are available on bacteria removal efficiencies and antibacterial properties of flocculants, which is one of the important requirements in water treatment work. Escherichia coli (E. coli) was selected as an example of a Gram-negative bacteria for testing the flocculating properties of a quaternary ammonium salt grafted chitosan (carboxymethyl chitosan-graft-poly[(2-methacryloyloxyethyl) trimethylammonium chloride] copolymer; i.e., CMC-g-PDMC). The effect of various flocculation parameters, including flocculant dosage, initial bacterial density, nutrient medium content, and pH were successively investigated. The experimental results indicated that, besides flocculation effects, CMC-g-PDMC also exhibited a bactericidal effect (not requiring additional treatment facilities). Moreover, the flocculation mechanisms were investigated via zeta potential measurements, floc observation, and three-dimensional excitation-emission matrix spectra analysis. Apart from its flocculating and settling effect, this chitosan-based material has bactericidal action through the breaking of bacterial cell walls by grafted quaternary ammonium salt.

Characterization of absorption and three-dimensional excitation-emission matrix spectra of chromophoric dissolved organic matter at the river inflow and the open area in Lake Taihu

应用吸收和三维荧光光谱对2007年夏季太湖入湖河口和大太湖开敞区有色可溶性有机物(CDOM)浓度及来源进行研究.结果表明,河口区和开敞区CDOM吸收系数a(355)存在显著空间差异,河口区明显大于开敞区(ANOVA,P<0.001),a(355)最大值出现在大浦河口和竺山湾漕桥河口附近,最小值出现在东太湖和胥口湾.a(355)与溶解性有机碳、化学耗氧量浓度存在显著正相关.所有样品一般都含有4个明显的荧光峰,包括1个可见光区的类腐殖质荧光C峰,1个紫外光区的类腐殖酸荧光A峰,2个类蛋白荧光B峰和D峰.河口区外源输入的类腐殖质荧光非常强,显著大于开敞区(ANOVA,P<0.05),而河口区和开敞区类蛋白荧光没有显著性差异,反映开敞区除外源河流输入外,内源生物降解等对类蛋白荧光贡献增加.在河口区B、C峰的比值r(B/C)小于1,均值为0.62±0.14、在开敞区r(B/C)除12#是0.92,其他值均大于1,均值为1.12±0.13,初步判断r(B/C)可以作为区分CDOM来源的重要参数.CDOM吸收a(355)与类腐殖质荧光C峰、A峰均存在极显著的正相关,而与类蛋白荧光相关性则明显下降,与D峰存在显著正相关,与B峰没有显著相关.;lower than 1 with the average value of 0.62±0.14, but was larger than 1 at sample 12 with the average value of 1.12±0.13. The r(B/C) can be preliminary used to distinguish the composition and source of CDOM. Significantly positive correlations were found between CDOM absorption coefficient and the fluorescence intensities of peaks A, C, D, but no significant correlation found with peak B